1. Field of the Invention
The present invention relates to a device for bending an optical fiber and receiving light used as an optical fiber identifier, a hot-line determination device, or the like. The device for bending an optical fiber and receiving light is used in optical fiber work such as laying, maintenance, and removal of optical fibers. The present invention particularly relates to a device for bending an optical fiber and receiving light that nondestructively performs for example a fiber core identification or a hot-line determination of an optical fiber such as an optical fiber core, an optical fiber strand, or an optical fiber code.
2. Description of the Related Art
This type of device for bending an optical fiber and receiving light is provided with a mechanism that holds an optical fiber, such as an optical fiber core, an optical fiber strand, or an optical fiber code, and bends it (fiber holding and bending mechanism), and an optical detector (light receiving element). In work such as laying, maintaining, and removing an optical fiber communication network, the device for bending an optical fiber and receiving light holds the optical fiber and deforms it by bending, and the optical detector detects the slight amount of communication light or a specific signal light that leaks from the bending portion to the outside. Thus, a hot-line determination of whether there is communication light, and a core identification for determining whether the optical fiber is a specific one, are performed nondestructively (see for example Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2006-235362).
FIG. 18 is a plan view showing a schematic configuration of a related device for bending an optical fiber and receiving light. FIG. 19A is a perspective view showing a projecting holding member of the device for bending an optical fiber and receiving light. FIG. 19B is a side view showing the structure in FIG. 19A viewed from the direction of arrow A.
As shown in FIG. 18, a device for bending an optical fiber and receiving light 101 includes a plate-like recessed holding member 110 having a recessed surface 111, and a projecting holding member 120 having a plate-like projection 122 forming a projecting surface 121 opposite the recessed surface 111. Generally, an optical fiber 140 is held between the recessed surface 111 of the recessed holding member 110 and the projecting surface 121 of the projecting holding member 120.
As shown in FIGS. 18 and 19A, the projecting surface 121 of the projection 122 of the projecting holding member 120 is formed on an outer peripheral side face of the projection 122, and formed as a shape along the recessed surface 111 of the recessed holding member 110.
The projecting holding member 120 can move parallel to a direction going toward and away from the recessed holding member 110. The projecting holding member 120 can move from an unclamped position, indicated by an imaginary line in FIG. 18, to a clamped position, indicated by a solid line in FIG. 18. As indicated by the solid line in FIG. 18, the clamped position is the position where the optical fiber 140 is held between the recessed holding member 110 and the projecting holding member 120 which has moved near to the recessed holding member 110. When the projecting holding member 120 is installed at the clamped position, the optical fiber 140 can be clamped (held) between the recessed surface 111 of the recessed holding member 110 and the projecting surface 121 of the projecting holding member 120; in addition, the optical fiber 140 can be bent. The recessed holding member 110 and the projecting holding member 120 constitute a fiber holding and bending mechanism that holds the optical fiber and applies a bend to it.
A light receiving element (optical detector) 130 of the device for bending an optical fiber and receiving light 101 in this example is assembled in the recessed holding member 110. To receive leak light from the optical fiber 140 which is held and bent by an optical fiber holding part 102, the light receiving element 130 is disposed such that a light acceptance surface 131 thereof is exposed at the recessed surface 111.
In the related art, the device for bending an optical fiber and receiving light 101 having the following structure is proposed. To accommodate optical fibers of various covered outer diameters, a fiber storage groove 103 having a groove width t is provided between the recessed surface 111 of the recessed holding member 110 and the projecting surface 121 of the projection 122 of the projecting holding member 120 installed at the clamped position. The groove width t of the optical fiber storage groove 103 is equal to or slightly larger than the covered outer diameter of the optical fiber having the covered outer diameter that is the largest (hereinafter ‘largest covered outer diameter’) among those being subjected to hot line determination and core identification (hereinafter ‘optical fiber with largest outer diameter’, denoted by reference numeral 141). Moreover, in the case of an optical fiber 142 which has a covered outer diameter that is smaller than the largest covered outer diameter (see FIG. 20; hereinafter ‘optical fiber with narrow diameter’), the projecting holding member 120 is moved from the unclamped position to the clamped position, and meanders into the optical fiber storage groove 103 having groove width t such that the optical fiber 142 is held in a bent state, whereby leak light can be generated (see for example paragraphs (0018), (0019), (0033), FIG. 1, and FIG. 2 of Patent Document 1).
As shown in FIG. 19B, the recessed surface 111 of the recessed holding member 110 and the projecting surface 121 of the projecting holding member 120 of the device for bending an optical fiber and receiving light 101 described above are formed perpendicular to the interval direction between the projecting surface 121 and the recessed surface 111 of the recessed holding member 110 (the left-right direction within the sheet in FIG. 19B).
As shown in FIGS. 19A and 19B, on the projection 122 of the projecting holding member 120, two rib-like protrusions 123a and 123b are provided on both sides of the projecting surface 121, and extend parallel to each other along the projecting surface 121. The projecting surface 121 is formed between this pair of protrusions 123a and 123b. 
When the projecting holding member 120 of the device for bending an optical fiber and receiving light 101 moves from the unclamped position (indicated by the imaginary line in FIG. 18) to the clamped position (indicated by the solid line in FIG. 18), the optical fiber storage groove 103 is formed between the recessed surface 111 and the projecting surface 121. Also, the tips of the pair of protrusions 123a and 123b protruding from the projection 122 abut to the recessed holding member 110, locking the projecting holding member 120 in the recessed holding member 110. As shown in FIG. 19A, light shielding members 124 stop disturbance light from being incident to the light receiving element 130. The light shielding members 124 are elastic bodies made from foam resin, and are attached at both ends of the extending direction of the projecting surface 121 of the projecting holding member 120. Thus the optical fiber storage groove 103 reliably forms a dark box.
As shown in FIG. 19B, in the device for bending an optical fiber and receiving light 101 described above, the distance s between the pair of protrusions 123a and 123b of the projecting holding member 120 is slightly larger than the covered outer diameter of the optical fiber with largest outer diameter 141. As already explained, the groove width t of the optical fiber storage groove 103 is equal to or slightly larger than the covered outer diameter of the optical fiber with largest outer diameter 141. Therefore, when the optical fiber with narrow diameter 142 is held between the recessed surface 111 of the recessed holding member 110 and the projecting surface 121 of the projecting holding member 120, as shown in FIG. 20, the position of the optical fiber with narrow diameter 142 in the width direction of the projecting surface 121 (in FIG. 20, the top-bottom direction within the sheet) is not fixed. As a result, the optical fiber 142 deviates greatly from the light acceptance surface 131 of the light receiving element 130, leading to problems such as only some of the leak light being coupled, or variation in the measurement of the leak light.